The invention concerns a safety or security light grid for monitoring a protected field or area.
Safety light grids protect persons and property against damage from dangerous machinery, such as bending presses, stamping machines, cutting tools, welding robots and the like. The safety light grid detects unauthorized entry into dangerous zones by monitoring the protected field covered by the light grid against penetration by an object. If the protected field is penetrated, the safety light grid generates an appropriate signal, which can be used, for example, to deactivate the machine.
Depending on the application, the light grid must be configured prior to its first use as well as after being replaced. By way of example, during a configuring process, the following might be set up:                whether the protective monitoring should be active or inactive,        whether a restart interlock should be active or inactive,        the operative range (long- or short-range) that should be set up,        what kind of signal should be fed to a diagnostic output,        which of several predetermined muting times should be selected.        
Light grids are known in which the configuration data are set up by means of wire bridges at the light grid itself or at a corresponding controller. This is time-consuming and labor-intensive and requires that certain processes be established in the device so that the set function does not change unintentionally in event of a simple error, such as a broken wire. This configuration, therefore, entails security risks and is not very comfortable.
So-called DIP switches are known for configuring purposes, but they have the drawback that they can only be serviced by a technician and they are situated on the inside of the device. It is therefore always necessary to open the device to make or change settings.
Safety light grids are also known which can be configured via a graphics user interface. For this, a computer or an SPS and a corresponding interface at the light grid for connection to the computer or the SPS are needed. Although the entry process is comfortable, a drawback is that this is costly because it requires an accessory device, such as a PC and a communication interface.